1. Field of the Invention
The present invention relates to a structure for joining electrical connection boxes. In particular, the invention relates to a joining structure between two electrical connection boxes installed in a vehicle.
2. Description of the Related Art
Electrical connection boxes installed in a vehicle may be joined together by locking structures provided thereon. For example, a relay box and a junction box provided with conventional joining structures are shown in FIGS. 3A-5B.
As shown in FIG. 3A, an upper cover 4 and a lower cover 3 respectively cover upper and lower portions of a body 2 of a relay box 1. A lock element 2a is provided on an exterior surface of the body 2. As shown in FIG. 3B, an engagement portion 5a is provided on an exterior surface of a junction box 5 at a position corresponding to the lock element 2a. As shown in FIGS. 4A and 4B, the relay box 1 is fixed on the exterior surface of the junction box 5 by engaging the lock element 2a with the engagement portion 5a. 
The junction box 5 is provided with a post-shaped terminal 6 on an upper surface thereof and with a wire guide channel 5c on a side surface thereof. A wire retaining element 5b projects from an intermediate portion of the wire guide 5c channel. A terminal 8 clamped to a terminal end of a wire w1 is connected to the post-shaped terminal 6. The wire w1 has a relatively large cross sectional area, such as 30 square millimeters. The wire w1 is arranged along the wire guide channel 5c and maintained therein by the wire retaining element 5b. 
However, when a relatively heavy relay box 1 is fixed on a junction box 5 by the lock element 2a and the engagement portion 5a, these locking portions are subjected to an excessive load which can lead to structural failure thereof. These locking portions can also be broken by an excessive load when a lock element 2a which is not properly aligned is slidingly inserted into an engagement portion 5a by force.
Another problem can occur when a wire w2 having a relatively small cross sectional area, such as 15 square millimeters, is connected to the post-shaped terminal 6 of the junction box 5. The space in the wire guide channel 5c is configured to receive a larger cross sectional area wire w1 therein, and the wire retaining element 5b is configured to maintain such a larger cross sectional area wire w1. Accordingly, when a smaller cross sectional area wire w2 is provided, as shown in FIGS. 5A and 5B, the direction of the smaller wire w2 cannot be controlled, and it is not maintained in the wire guide channel 5c. 
The present invention has been made in view of the above-described problems. Accordingly, it is an object of the present invention to provide a structure for joining electrical connection boxes, which structure prevents material failure of locking portions and maintains the directions of wires having different diameters or cross sectional areas.
According to one aspect of the present invention, there is provided a structure for joining electrical connection boxes. The structure includes a lock element provided on a first electrical connection box and an engagement portion provided on a second electrical connection box. The lock element and the engagement portion are configured for locking engagement therebetween. The structure also includes at least one guide portion provided on the first electrical connection box adjacent to the lock element, and at least one guide rail provided on the second electrical connection box adjacent to the engagement portion. The at least one guide portion and the at least one guide rail are configured such that the at least one guide rail is slidingly received within the at least one guide portion. Further, the second electrical connection box includes a wire guide channel provided adjacent to the at least one guide rail, and the at least one guide portion functions as a guide wall for maintaining a wire within the wire guide channel by controlling a direction of the wire.
According to a further aspect of the present invention, the at least one guide portion includes a first guide portion and a second guide portion respectively provided on opposite sides of the lock element, and the at least one guide rail includes a first guide rail and a second guide rail respectively provided on opposite sides of the engagement portion. The first guide rail is slidingly received within the first guide portion, and the second guide rail is slidingly received within the second guide portion.
According to a further aspect of the present invention, the wire guide channel is provided adjacent to the first guide rail, and the first guide portion functions as a guide wall for maintaining the wire within the wire guide channel by controlling a direction of the wire.
According to a further aspect of the present invention, during joining of the first electrical connection box and the second electrical connection box, the first guide portion engages the first guide rail and the second guide portion engages the second guide rail prior to the lock element engaging the engagement portion.
According to a further aspect of the present invention, during joining of the first electrical connection box and the second electrical connection box, the first guide portion engages the first guide rail prior to the second guide portion engaging the second guide rail.
According to a further aspect of the present invention, a leading portion is provided on the first electrical connection box for aligning the at least one guide portion with the at least one guide rail during joining of the first electrical connection box and the second electrical connection box.
According to a further aspect of the present invention, a wire retaining element is provided on the second electrical connection box, the wire retaining element extending partially around the wire guide channel for maintaining a wire within the wire guide channel.
According to a further aspect of the present invention, the at least one guide portion and the wire retaining element engage different portions of a wire within the wire guide channel.
According to another aspect of the present invention, there is provided a structure for joining electrical connection boxes. The structure includes a lock element provided on a first electrical connection box and an engagement portion provided on a second electrical connection box. The lock element and the engagement portion are configured for locking engagement therebetween. The structure also includes at least one guide portion provided on the first electrical connection box adjacent to the lock element, and at least one guide rail provided on the second electrical connection box adjacent to the engagement portion. The at least one guide portion and the at least one guide rail are configured such that the at least one guide rail is slidingly received within the at least one guide portion.
According to a further aspect of the present invention, the at least one guide portion includes a first guide portion and a second guide portion respectively provided on opposite sides of the lock element, and the at least one guide rail includes a first guide rail and a second guide rail respectively provided on opposite sides of the engagement portion. The first guide rail is slidingly received within the first guide portion, and the second guide rail is slidingly received within the second guide portion.
According to a further aspect of the present invention, the second electrical connection box includes a wire guide channel provided adjacent to the first guide rail, and the first guide portion functions as a guide wall for maintaining a wire within the wire guide channel by controlling a direction of the wire.
According to a further aspect of the present invention, a wire retaining element is provided on the second electrical connection box, the wire retaining element extending partially around the wire guide channel for maintaining a wire within the wire guide channel.
According to a further aspect of the present invention, the first guide portion and the wire retaining element engage different portions of a wire within the wire guide channel.
According to a further aspect of the present invention, during joining of the first electrical connection box and the second electrical connection box, the first guide portion engages the first guide rail and the second guide portion engages the second guide rail prior to the lock element engaging the engagement portion.
According to a further aspect of the present invention, during joining of the first electrical connection box and the second electrical connection box, the first guide portion engages the first guide rail prior to the second guide portion engaging the second guide rail.
According to a further aspect of the present invention, a leading portion is provided on the first electrical connection box for aligning the at least one guide portion with the at least one guide rail during joining of the first electrical connection box and the second electrical connection box.
As described above, the guide portion is provided on the first electrical connection box adjacent to the lock element, and the lock element is engaged with the engagement portion while the guide portion is slidingly fitted on the guide rail of the second electrical connection box. Accordingly, the lock element is aligned in the correct position by the guide portion and fixed with the engagement portion. The destruction of the lock element and engagement portion during engagement can be avoided. After engaging the lock element and the engagement portion, since the guide portion as well as the lock element support the weight of the first electrical connection box, the guide portion reinforces the lock element, and the load on the lock element and engagement portion can be dispersed.
Further, since the guide portion is located adjacent to the wire guide channel of the second electrical connection box, even though the diameter or cross sectional area of the wire to be arranged along the wire guide channel is much smaller than that of the wire guide channel, it is possible to control the direction of the small wire along the wire guide channel because the guide portion located opposite the wire guide channel functions as a guide wall for the wire.
As described above, when the first electrical connection box is joined to the second electrical connection box, the first electrical connection box is loosely positioned by the first guide portion fitted on the first guide rail, and then completely positioned by the second guide portion fitted on the second guide rail. Thereafter, the lock element can be engaged with the engagement portion without shifting. The destruction of the lock element and the engagement portion can be avoided.
The first electrical connection box is attached to the second electrical connection box at three points by the lock portions, the first guide portions and the second guide portions. Thus, it is possible to reinforce the lock portions by dispersing the load force.